Throughout the mechanized world the use of hydraulic systems abound, from heavy earth moving equipment, aircraft control systems, even entertainment rides at amusement parks. All of these depend on the integrity of the system's components for safe completion of their task.
To date there has been limited focus on the need for enhancing the safety of these potentially dangerous systems. Hydraulic or liquid pressurized systems often experience line failure such as a sever leak or break. When the failure occurs, other damage to peripheral equipment, environmental contamination and personal injury can also take place. For example, the hydraulic pump, still running, can empty a reservoir and then run dry causing the pump to be destroyed. Hydraulic fluid would be pumped onto the ground causing detrimental effects to the environment. If the line failure was a complete break, the resultant whiplash could seriously injure workmen standing immediately nearby, and if the line failure was a severe leak the spraying fluid could cause other types of harm to personnel. Hydraulic fluid could also spew onto diesel engine manifolds, or other hot surfaces or electric circuits, causing a fire to completely destroy the surrounding equipment. It is, therefore, desirable to provide adequate safety precautions to guard against these hazards.
Problems associated with these hydraulic fluid spills from broken lines have only recently been addressed due to heightened awareness on the part of environmental groups and actions taken by the Environmental Protection Agency, Department of Environmental Quality, the U.S. Forest Service and other interested parties.
Currently, there are many different types of equipment in use with limited or no safeguards. For instance, the logging industry utilizes hydraulic boom trucks for the loading of downed timber. If during operation, a hydraulic line breaks, not only is the load dropped but the resultant high pressure spray of fluid can contaminate several hundred square feet of forest area which results in a substantial economic cost to clean up, as required by forestry officials.
There are many stop-gap approaches to the problem. Currently there are several types of single devices used by industry which will actuate when line failure occurs. One such device is called a velocity fuse that can be used to temporarily stop pressurized flow because of the increased fluid velocity that would be flowing across the unit's seat when failure occurred. A more recent development, also called a hydraulic fuse, operates primarily by pressure loading an internal piston, and the drop in operating pressure as seen at its outlet port. Another singular valve design sees line pressure acting upon a semi-balanced piston that is held open by a shear pin. When line failure occurs the piston's loading force is increased due to increased differential pressure, thus destroying the shear pin and providing the means for the valve to close. These designs are singular in that they have provisions for only two flow ports, i.e., one inlet and one outlet port. By design they are flow-limited and therefore have limited application.
On the other hand, large cross-country pipe lines utilize two-way (either on or off) valves that utilize sensing lines. These units are not usually flow-limited but could not be installed into normal hydraulic service due, in part, to their extremely large physical size and their mandatory use of upstream and downstream pressure sensing instrument lines. At best, these designs could only partially solve the problem at hand and none as yet address, not only the fluid loss issue, but the continued operation of the hydraulically-operated equipment.
It is the objective of this invention to provide improved techniques and apparatus to control the detrimental effects of hydraulic system line failure.
It is another objective of this invention to reduce the time, effort, paperwork, and economic cost which is associated with hydraulic fluid spills and the resulting clean up actions that are required of system operators.
It is yet another objective of this invention to significantly reduce the risk of injury to the thousands of personnel who labor on or around equipment or machines that are controlled or operated by high pressure hydraulic systems.